Patent US5150053A successfully refreshed from Google Patents.
US5150053A
Expired / Lapsed
US
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Magnetic resonance imaging of short T2 species with improved contrast
Assignee: Leland Stanford Junior University
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Filing: 1991-01-25
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Granted: 1992-09-22
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Expires: 2011-01-25
Abstract
Abstract Magnetic resonance signals for imaging species having short spin-spin relaxation times (T 2 ) are obtained without the need for a refocusing lobe. A series of RF excitation pulses are applied to the species with magnetic resonance signals being detected after each RF excitation pulse is applied. The magnetic resonance signals are then combined to provide the imaging signals. In one embodiment, each RF excitation pulse is half of a conventional slice-selective pulse with each pulse being slewed to zero. Contrast between the imaged short T 2 species and longer T 2 species can be enhanced by first applying an RF signal having sufficient amplitude to excite the longer T 2 species but insufficient amplitude to excite the short T 2 species whereby the longer T 2 species are tipped by the RF signal. A magnetic gradient can then be applied to dephase the tipped nuclei of the longer T 2 species. The imaging signals are then obtained from magnetic resonance signals from the short T 2 species.
Inventors
- 👤 John M. Pauly
- 👤 Steven M. Conolly
- 👤 Dwight G. Nishimura
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 04:55
CPC Classifications
G; G01; G01R; G01R33/00; G01R33/20; G01R33/44; G01R33/446; G01R33/48; G01R33/50; G01R33/54; G01R33/56
Claims Analysis
Total Claims: 15
Claim 1
Independent Claim
169 words
A method of obtaining slice-selective magnetic resonance signals for imaging short T 2 species while suppressing longer T 2 species comprising the steps of (a) applying a static magnetic field (B o ) to a body thereby aligning nuclear spins, (b) applying an RF pulse to said body, said RF pulse having sufficient amplitude to excite the longer T 2 species but insufficient amplitude to excite the short T 2 species, (c) applying a modulated magnetic gradient (G(t)) to said body, (d) applying a first RF excitation pulse (B 1 (t)) to said body to tip said nuclear spins, (e) detecting first magnetic resonance signals from said body, (f) applying a second RF excitation pulse (B 1 (t)) to said body to tip said nuclear spins, said first RF excitation to pulse and said second RF excitation pulse each being half of a conventional slice-selective pulse, (g) detecting second magnetic resonance signals from said body, and (h) combining said first magnetic resonance signals and said second magnetic resonance signals.
Claim 2
Independent Claim
169 words
A method of obtaining slice-selective magnetic resonance signals for imaging short T 2 species while suppressing longer T 2 species comprising the steps of (a) applying a static magnetic field (B o ) to a body thereby aligning nuclear spins, (b) applying an RF pulse to said body, said RF pulse having sufficient amplitude to excite the longer T 2 species but insufficient amplitude to excite the short T 2 species, (c) applying a modulated magnetic gradient (G(t)) to said body, (d) applying a first RF excitation pulse (B 1 (t)) to said body to tip said nuclear spins, (e) detecting first magnetic resonance signals from said body, (f) applying a second RF excitation pulse (B 1 (t)) to said body to tip said nuclear spins, said first RF excitation to pulse and said second RF excitation pulse each being half of a conventional slice-selective pulse, (g) detecting second magnetic resonance signals from said body, and (h) combining said first magnetic resonance signals and said second magnetic resonance signals.
Claim 3
Dependent Claim
43 words
The method as defined by claim 1 wherein each of said RF excitation pulses is slewed to zero at a slew rate, S, and said modulated magnetic gradient is slewed to zero as each of said RF excitation pulses is slewed to zero.
Claim 4
Dependent Claim
23 words
The method as defined by claim 2 wherein said modulated magnetic gradient is ##EQU12## and each of said RF excitation pulses is ##EQU13##
Claim 5
Dependent Claim
32 words
The method as defined by claim 1 wherein step (b) tips the longer T 2 species away from one axis while the short T 2 species remain aligned along said one axis.
Claim 6
Dependent Claim
27 words
The method as defined by claim 4 wherein step (b) further includes applying a magnetic gradient along said one axis thereby dephasing the longer T 2 species.
Claim 7
Dependent Claim
172 words
Apparatus for obtaining slice-selective magnetic resonance signals for imaging short T 2 species comprising (a) means for applying a static magnetic field (B o ) to a body thereby aligning nuclear spins, (b) applying an RF pulse to said body, said RF pulse having sufficient amplitude to excite the longer T 2 species but insufficient amplitude to excite the short T 2 species, (c) means for applying a modulated magnetic gradient (G(t)) to said body, (d) means for applying a first RF excitation pulse (B 1 (t)) to said body to tip said nuclear spins, (e) means for detecting first magnetic resonance signals from said body, (f) means for applying a second RF excitation pulse (B 1 (t)) to said body to tip said nuclear spins, said first RF excitation pulse and said second RF excitation pulse each being half of a conventional slice-selective pulse, (g) means for detecting second magnetic resonance signals from said body, and (h) means for combining said first magnetic resonance signals and said second magnetic resonance signals.
Claim 8
Dependent Claim
172 words
Apparatus for obtaining slice-selective magnetic resonance signals for imaging short T 2 species comprising (a) means for applying a static magnetic field (B o ) to a body thereby aligning nuclear spins, (b) applying an RF pulse to said body, said RF pulse having sufficient amplitude to excite the longer T 2 species but insufficient amplitude to excite the short T 2 species, (c) means for applying a modulated magnetic gradient (G(t)) to said body, (d) means for applying a first RF excitation pulse (B 1 (t)) to said body to tip said nuclear spins, (e) means for detecting first magnetic resonance signals from said body, (f) means for applying a second RF excitation pulse (B 1 (t)) to said body to tip said nuclear spins, said first RF excitation pulse and said second RF excitation pulse each being half of a conventional slice-selective pulse, (g) means for detecting second magnetic resonance signals from said body, and (h) means for combining said first magnetic resonance signals and said second magnetic resonance signals.
Claim 9
Dependent Claim
42 words
Apparatus as defined by claim 6 wherein each of said RF excitation pulses is slewed to zero at a slew rate, S, and said modulated magnetic gradient is slewed to zero as each of said RF excitation pulses is slewed to zero.
Claim 10
Dependent Claim
22 words
Apparatus as defined by claim 7 wherein said modulated magnetic gradient is ##EQU14## and each of said RF excitation pulses is ##EQU15##
Claim 11
Dependent Claim
32 words
Apparatus as defined by claim 6 wherein said (b) means tips the longer T 2 species away from one axis while the short T 2 species remain aligned along said one axis.
Claim 12
Dependent Claim
35 words
Apparatus as defined by claim 9 and further including means for applying a magnetic gradient along said one axis after said RF pulse is applied to said body thereby dephasing the longer T 2 species.
Claim 13
Dependent Claim
133 words
In imaging short T 2 species in a body while suppressing longer T 2 species in the body using magnetic resonance imaging, a method on enhancing image contrast between the short T 2 species and the longer T 2 species comprising the steps of (a) applying a static magnetic field (B o ) to the body thereby aligning nuclei along an axis (z), (b) applying an RF pulse to said body, said RF pulse having sufficient amplitude to excite the longer T 2 species but insufficient amplitude to excite the short T 2 species, whereby nuclei of the longer T 2 species are tipped away from said axis while the short T 2 species remain aligned along said axis, and (c) thereafter detecting magnetic resonance signals for imaging the short T 2 species.
Claim 14
Dependent Claim
133 words
In imaging short T 2 species in a body while suppressing longer T 2 species in the body using magnetic resonance imaging, a method on enhancing image contrast between the short T 2 species and the longer T 2 species comprising the steps of (a) applying a static magnetic field (B o ) to the body thereby aligning nuclei along an axis (z), (b) applying an RF pulse to said body, said RF pulse having sufficient amplitude to excite the longer T 2 species but insufficient amplitude to excite the short T 2 species, whereby nuclei of the longer T 2 species are tipped away from said axis while the short T 2 species remain aligned along said axis, and (c) thereafter detecting magnetic resonance signals for imaging the short T 2 species.
Claim 15
Dependent Claim
31 words
The method as defined by claim 11 and including after step (b) the step of applying a magnetic gradient along said one axis thereby dephasing the longer T 2 species nuclei.
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
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| 3.5 Years (Year 4) | 1995-09-22 | 1996-03-23 | 1996-09-22 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1999-09-22 | 2000-03-23 | 2000-09-22 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2003-09-22 | 2004-03-23 | 2004-09-22 | $7700.00 | Window Closed / Lapsed |